Dining and Cooking
What causes this extraction shape?
In Espresso

What causes this extraction shape?


Please excuse my crude drawing… hoping someone can extrapolate from this bad explanation.

Nine times out of ten when I pull a shot it looks like fig. 1. But once in a while fig. 2 will happen and I am curious:

  1. What causes this?

  2. Do we like it? (Is it good or bad)

by yodee_21

27 Comments

  1. No-Antelope3774

    Two things

    One: very fresh beans, and it’s co2

    Two: excess heat – if you have a single boiler and have been using the steam function and turn it on early.

  3. WAtHome

    Fig2: CO2 from beans that are too fresh. Wait a week longer and it’ll look like Fig1. Beans tastes best starting from about 10 days from roasting (dark), 15 days (medium), and 20 days (light)

  4. haipr

    How fresh are your used beans?
    This also happens if your coffee beans had been roasted not too long ago (e.g. 5 days ago).
    Happened quite a lot of times especially with fresh 100% robusta beans.
    This means, the beans need to gas out a few more days.

  5. Gypsydave23

    Great diagram!
    I prefer the rat tail in figure 1. I usually have to grind very fine and sometimes dim my pump, but it seems sweeter and tastier to me. I wouldn’t be upset with figure 2, and they look nice in photos, but figure 1 is what I go for. Maybe drying off your portafilter between shots will help if you are doing the same thing every time ? I suspect having a wet basket might make it spread out like that

  6. yodee_21

    Okay, can’t edit the body so I’ll add this in a comment since a lot of people have commented on the freshness of the beans… fig. 2 just recently happened on a bag I’m half way through consuming… so I feel that it cannot be that? Interested by the temperature comments…

  7. TechnicalDecision160

    I kinda likes your drawings. May I frame them?

  10. cabennett8585

    Would it be possible for this to happen with beans that are burnt? Only time I got that shape (fg 2) the beans smelled and tasted a bit burnt

  13. DonkeyWorker

    To prevent the backdoor slamming shut.

  16. 420BongMaster

    Gassy fresh beans. Let them sit for a while to off gas

  17. KettchupIsDead

    Almost always just an excess of CO2 in the beans

  18. Mobile_Pilot

    Fig2 suggests the Flow is higher than Fig1.

    A relatively higher Flow can be a result of:
    – lower dose of coffee grounds in the basket
    – coarser grounds
    – higher temperature
    – weaker tamping force
    – water pump maximum pressure and water debit capability
    – no adoption of top metal filter
    – no adoption of bottom paper filter
    – shallower height of portafilter
    – bigger and/or more holes underneath portafilter
    – beans roasted a longer time ago
    – beans less well conserved (hotter storage temperature and/or higher exposure to light)
    – broader shaped particle’s size distribution
    – more fines as a % of total particles

    Two last considerations: I haven’t mentioned channeling because it could happen in both illustrations, It is related to puck density homogeneity and some factors mentioned above. Second, I’m unsure if roast level is an independent driver of higher flow by itself or if it is fully correlated with the factors mentioned already.

  19. callMeBorgiepls

    Go to ur sink, and let just water go into the porterfiler. Slow enough so it doesnt overflow. It will have a shape roughly like fig 1. Thats the baseline.

    If you add coffee that is fresh and gives a good crema, and pressure, then there will be foam, a very thick shot generally, and therefore the flow is slower, and the cone get broader.

  21. Jealous-Kiwi-1161

    1 is when you grind very fine. 2 when you grind very coarse

  25. FrontWork7406

    1. Gas. CO2. It looks sexy, but it actually makes extraction more difficult. Coffee is porous, so if you imagine water migrating through the grounds as if it is a 1-way road, the water can’t move down through the coffee is CO2 is escaping. I don’t use a coffee on espresso unless it’s at least 2 weeks old, if I can help it.

    2. We don’t have to like the same things. You can be an individual and choose to like aesthetics over taste. Most people tend to eat with their eyes. In the psychology of user experience, this is called the law of aesthetic usability.